Refactor menu bar code

Signed-off-by: Niklas Koep <niklas.koep@gmail.com>
Remove option to hide playlist tabs

Signed-off-by: Niklas Koep <niklas.koep@gmail.com>
Add BlaUIManager instance to Blaplay singleton

Signed-off-by: Niklas Koep <niklas.koep@gmail.com>
Make BlaView class a singleton

Signed-off-by: Niklas Koep <niklas.koep@gmail.com>